Air operated braking systems have long been utilized to control commercial vehicles such as trucks and trailers, which typically have large gross vehicle weights in a safe and effective manner. The considerable inertial mass of these heavy-duty vehicles in combination with the high speeds at which they travel requires a braking system which responds rapidly with substantial braking power. A spring brake actuator is used in air operated braking systems to provide the force necessary for braking a heavy-duty vehicle.
In a typical spring brake system, braking force may be applied in a number of ways. For normal braking operation, compressed air is introduced into the brake chamber, which co-acts with a diaphragm, such as, for example, an elastomeric diaphragm, and a push rod to apply braking force. For emergency and/or parking brake applications, a power spring stores potential energy and exerts the large force required for braking in case of loss of air pressure or air pressure failure. During normal driving operation, compressed air acts on a diaphragm to compress the power spring to maintain the braking system in a released position. When the compressed air is released, the force of the power spring overcomes the force of the compressed air such that the power spring expands co-acting with the diaphragm and push rod. This in turn, applies a braking force in case of failure of the system air pressure or exhaustion of compressed air while the vehicle is not in operation or is parked.
A loss of compressed air in typical air brake systems means that the power spring applies a braking force to prevent the vehicle from moving. Accordingly, some systems have provided for an emergency/supply pressure line to the braking system such that, in the event of a loss of air pressure on the primary service/control line to the brake system, compressed air will still flow to the brake via an emergency/supply air pressure line. While this configuration will provide a functioning system in the event of catastrophic failure of the service/control line, this system will not provide information to the driver regarding the efficiency of the braking system. For example, the service/control line may suffer from a leaky connection causing substantial leaking of the compressed air. There may be enough air pressure in the system to allow for operation of the vehicle, but the vehicle may suffer from brake drag, meaning the air pressure is not high enough to completely overcome the power spring such that the brake is partially applied during normal driving operation.
Many problems relating to the air supply to both the service and emergency systems occur with prior art systems. For example, with current systems, the emergency/supply line extends to the braking mechanism adjacent to the wheel, and is therefore, subject to damage. If the emergency/supply line becomes damaged, there is no way to determine this if the service/control line continues to function, even if it is only partially functional. Likewise, incorrect connection of supply hoses when a braking system is removed for servicing and re-installed may occur. If, for example, the emergency/supply line is incorrectly re-installed, upon failure of the primary supply line, the braking system will not function. Another air related problem that exists for prior art systems is the provision of service/control air pressure to the trailer when the brakes are not applied. If, for example, there is an air leak from the tractor to the trailer on the service/control pressure line at all times. Still another problem that prior art systems face is the service/control and emergency/supply lines can deliver inadequate pressure due to obstructions or leaks within the air lines. If, for example, moisture in a pressure line freezes and obscures the air pressure line or an air line cracks or gets damaged by road debris.
Another problem that prior art systems face is the provision of stoplight power to the trailer when the brakes are applied. If, for example, the stoplight switch is faulty, stoplight power can be present at the trailer without service/control pressure.
Additional problems with prior art systems include the lack of input data to the brake monitor. For example, prior art systems do not provide wheel speed data on the power line from a faulty ABS controller. If, for example, the ABS controller has failed or the wheel speed sensors are faulty or have an excessive gap with the exciter ring, then the ABS ECU cannot detect or transmit individual wheel speeds. Similarly, incorrect connection of the 7-conductor electrical connection to the towed vehicle leads to problems in prior art systems. If, for example, the connection is an open circuit, the Anti-Lock Braking System (ABS) will not function as well as the stoplights during a braking event.
Still another problem that prior art systems face is incorrect air connections to the dolly that connects two trailers together. Each dolly has one service/control and one emergency/supply pressure line to the lead trailer as well as one service/control and one emergency/supply pressure line to the towed trailer. There are twenty-four different combinations these pressure lines on the dolly can be connected between two trailers with only one combination being correct. Incorrect connection of service/control or emergency/supply hoses will cause a various number of failure conditions. One being no brakes when the service/control line has pressure the other being wheel lockup when the emergency/supply line has no pressure. These failure conditions can be on any one or all wheels of the vehicle. Likewise, another problem that prior art systems face is incorrect connection of supply hoses when a braking system is removed for servicing and re-installed. If, for example, the emergency/supply line is incorrectly re-installed, upon failure of the primary supply line, the braking system will not function. These failure conditions can be on any one or all wheels of the vehicle.
Another problem that prior art systems face is the service/control and emergency/supply line glad-hand shut-off valves at the rear of the trailer. These valves require an open state when towing another vehicle and require a closed state when they are the rear vehicle on a single or multiple trailer combination. Incorrect positioning of the valves will cause the alarm, warning lamp or wireless message and/or signal to be generated. If, for example, the service line glad-hand shut-off valve is shut off to the towed vehicle causing a failure of the service/control line, the service braking system will not function.
As braking systems become more integrated, pneumatic systems are increasingly including electrical components and distribution lines for transmitting power and data. Various electrical components require electrical power to operate correctly including, lamps, electronic circuits, ABS (Anti-lock Braking System) and EBS (Electronic Braking System) to name a few. A loss of electrical power may cause these systems to be non-functional, which would generally be apparent. However, in a situation with reduced or relatively lower power, the systems may not be completely prevented from functioning, but system function and operation may be substantially impaired.